Vibratory conveyor devices are in widespread use in view of their versatile material-handling capabilities. Such devices typically include a generally elongated trough or bed which is vibrated by an associated drive system so that material is conveyed along the length of the trough.
In typical constructions of so-called two mass vibratory conveyors, a support structure or base of the conveyor includes a pair of longitudinal base members typically constructed from heavy wall tubing or solid plate steel to obtain the desired structural characteristics, and in part to obtain the specifically desired weight relationship between the trough and the support structure. Generally speaking, the total stroke of the conveyor is divided between the trough and the support structure, including the base members, in inverse proportion to their mass ratio. Since it is desirable to minimize the vibratory motion of the support structure (to thereby facilitate isolation of the conveyor's transmitted vibration to surrounding structures), the support structure, including the base members, is typically more than twice the weight of the trough structure, and in some cases, as much as eight times or more in weight. In some designs, it is often necessary to add ballast weight to the support structure in order to obtain the desired base stroke. Some vibratory conveyor designs, like the base-excited conveyor, are inherently advantageous from an overall weight perspective, because the stroke of the base is dependent upon the tuning of the conveyor's spring/mass system with respect to the desired operating frequency.
In order to maintain the required stiffness of the support structure, and to prevent unwanted torsional and vertical bending modes of the structure that may be excited at the operating frequency of the conveyor, cross-members, typically made from steel tubes, angle, or channel sections, are connected between the longitudinal base members to form a stiff ladder-like frame construction. It is common practice to connect the spring-mounting elements of the conveyor at the points where these cross-members attach to the longitudinal base members to thereby take advantage of the structural support provided by the cross-members.
Experience has shown that one problem encountered with current conveyor designs is the cost associated with the weight, construction, and complexity of the support structure. This problem is aggravated if an all stainless steel construction is mandated by specific sanitation requirements for the conveyor application. While the base-excited conveyor design is more advantageous with respect to such considerations, it will be appreciated that it is desirable to further reduce the overall weight of the machine, while maintaining the same operating capacity, thus providing desired operating efficiencies.
To this end, efforts have been made to develop a base-excited conveyor construction employing the lightest possible support structure construction. However, because of the lightweight formed sheet metal sections used in this construction, it is necessary to avoid fatigue failure at the spring connections to the base members which could result from concentrated shear and bending loads to which the base members are subjected at the spring connections. While previous constructions have employed so-called "scab" reinforcing plates, castings, blocks, or the like for longitudinally spreading the loads to which the mounting blocks for the springs are subjected, such constructions necessarily result in a heavier construction. This, of course, is self-defeating in the context of providing a relatively lightweight base-excited conveyor construction.
The present invention contemplates an improved vibratory conveyor construction, including an improved support structure which can be configured from relatively lightweight components, thus facilitating economical manufacture and operating efficiency.